Question: Solve for $x$ and $y$ using substitution. ${2x-y = -7}$ ${x = -y-11}$
Answer: Since $x$ has already been solved for, substitute $-y-11$ for $x$ in the first equation. ${2}{(-y-11)}{- y = -7}$ Simplify and solve for $y$ $-2y-22 - y = -7$ $-3y-22 = -7$ $-3y-22{+22} = -7{+22}$ $-3y = 15$ $\dfrac{-3y}{{-3}} = \dfrac{15}{{-3}}$ ${y = -5}$ Now that you know ${y = -5}$ , plug it back into $\thinspace {x = -y-11}\thinspace$ to find $x$ ${x = -}{(-5)}{ - 11}$ $x = 5 - 11$ ${x = -6}$ You can also plug ${y = -5}$ into $\thinspace {2x-y = -7}\thinspace$ and get the same answer for $x$ : ${2x - }{(-5)}{= -7}$ ${x = -6}$